As is known in the art, in array antennas, performance is often limited by the size and bandwidth limitations of the antenna elements which make up the array. Further, packaging volume constraints often require low profile antenna structures. Improving bandwidth while maintaining a low profile, which meets volume constraints, enables array system performance to meet bandwidth, scan, and volume packaging requirements of next generation communication systems, such as software defined or cognitive radio.
Attempts have been made to fabricate low profile antenna elements and array antennas. Such array antennas include an array of tightly coupled dipole elements which approximates the performance of an ideal current sheet, as well as so-called “bunny ear” antennas, and tightly coupled patch arrays. While these antenna element designs are all low profile, they either fail to operate over a desired bandwidth or require complex feed structures to support either dual linear or circular polarizations (e.g. requiring external components difficult to fit within the antenna element of an array antenna). Other antenna elements, such as Vivaldi notch antenna elements, can provide a relatively wide bandwidth, but are not low profile.